Devices that separate gases, liquids, and solids work on a variety of principles, two of which are gravity and centrifugal force. Conventional gravity type separators have been widely used to separate a gas from a liquid (or vice versa) on land-based crude oil and gas process plants. These separators are generally quite large and heavy because the separation takes place over a longer period of time and to do so efficiently you need a larger volume of space. Examples of this type of separator are: Kotzebue, U.S. Pat. No. 1,782,783; Pittman, U.S. Pat. No. 1,994,110; Orrell, U.S. Pat. No. 2,767,802; and Ray, U.S. Pat. No. 2,887,174.
Other separators work by centrifugal force. Generally they accelerate the division of gas and liquid by increasing the separatory centrifugal forces. When a liquid/gas mixture is spun, the heavier object, i.e., the oil, makes its way through the mixture to the outermost point and the lighter gas migrates inward. Examples of liuqid/gas centrifugal force separators are: Moore, U.S. Pat. No. 3,713,279; Kartinen, U.S. Pat. No. 3,810,347; Reed et al., U.S. Pat. No. 4,035,171; Beattie, U.S. Pat. No. 4,070,168 and Hodgson, U.S. Pat. No. 4,187,089. Examples of sand centrifugal separators are: Stavenger, U.S. Pat. No. 3,259,246; Hill U.S. Pat. Nos. 2,539,019, 2,566,662 and 1,919,653; Hruby, Jr., U.S. Pat. No. 3,067,876; and Hume, U.S. Pat. No. 3,045,828.
Conventional gravity type separators have been widely used to separate gas from liquid (or vice versa) on land-based crude oil and gas process plants. The same equipment has also been employed on offshore production platforms in spite of significant associated installation costs due to its large space and weight requirements. It requires a large pressure vessel to provide a long enough retention time in order to separate and settle, by gravity, small liquid particles in the gas/liquid mixture. Similarly, the centrifugal force oil/gas separators have not been perfected for offshore use either.
Furthermore, the floating production platform, such as a tension leg platform, floating barge, or a semisubmersible, will experience significant motions due to constant wave, current, and wind forces. The separation performance of a gravity separator will be hampered significantly due to the turbulence generated by sloshing wave motions of the liquid caused by the vessel motions. To correct this problem even larger and heavier pressure vessels will be required to cope with this problem and consequently further costs will be increased further for the equipment and the structure supporting it.
One solution to the problem is to incorporate a set of double hydrocyclones inside a conventional horizontal (or vertical) gravity separator. This design takes advantage of both the centrifugal force of the hydrocyclone and gravity as in a conventional separator. Most of the basic separation will be done by the hydrocyclone so that the size of the pressure vessel will be greatly reduced. The result is a compact, lightweight separator at a significantly reduced equipment weight. Because the installation space requirement and the total associated costs are low, this system is suitable for offshore production platforms, in particular, for a floating production platform application.
As a result, it is the principal object of this invention to create a device for gas/liquid separation. It is a further object of this invention to create a device that is lighter, smaller, and cheaper than current gas/liquid separators.